The aim is to obtain information leading to an improved understanding of enzymatically catalyzed glycosylation, and of the relationship of glycoside hydrolases to glycosyl transferases. Glycosylation is the process whereby the many complex saacharides of living organisms are synthesized from, and degraded to, sugar components. A novel experimental approach, developed in our laboratory, is being used to gain basic knowledge of a new type about the catalytic capabilities of enzymes considered to be well characterized by traditional studies with glycosidic substrates. This approach consists of the study of glycosylation reactions that occur without glycosidic bond cleavage. Our recent work has shown, for example, that "exo-alpha-glucan hydrolases" can attack both alpha- and beta-forms of appropriate glycosyl fluorides. Studies still in progress reveal that such enzymes, long believed to catalyze only the hydrolysis of alpha-glucosidic linkages, have a second (nonhydrolytic) mode of action, stereospecifically complementary to the well known (hydrolytic) mode. A new view of the mechanism of these enzymes has emerged, emphasizing the functional flexibility of their catalytic groups. We plan to further use specific glycosyl fluorides to study the extent to which classic endo-glycanases and glucanosyl transferases can catalyze polymerative synthetic reactions in which water is kept out of a succession of steps. The ability of carbohydrases to create anomeric asymmetry anew from substrates lacking alpha- or beta-anomeric configuration, was recently demonstrated in our laboratory. This phenomenon will be further studied, using enolic glycosyl donors of different types, as a means of more clearly defining the nature of the glycosylation process and of the mechanism of its catalysis.